1. Field of the Invention
The present invention relates to a copier, facsimile apparatus, printer or similar image forming apparatus and more particularly to a cleaning device included in an image forming apparatus for removing toner particles left on the surface of an image carrier after image transfer.
2. Background of the Invention
A cleaning device of the type removing toner particles left on the surface of a photoconductive drum or similar image carrier with a cleaning blade is extensively used in image forming apparatuses. The cleaning blade is, in many cases, formed of metal or rubber or similar elastic material.
A cleaning blade formed of metal has a drawback that the edge portion of the blade, contacting the surface of the image carrier, deforms little and therefore fails to closely contact the surface of the image carrier if the machining accuracy of the edge portion is low or if fine irregularities exist on the above surface. As a result, toner grains are apt to slip through a small gap formed between the edge portion of the cleaning blade and the surface of the image carrier, bringing about defective cleaning.
By contrast, a cleaning blade formed of rubber or similar elastic material has an edge portion deformable along the surface of an image carrier and can therefore closely contact the surface of the image carrier even if the machining accuracy of the edge portion is relatively low or even if fine irregularities exist on the above surface. Such a cleaning blade allows a minimum of toner grains to slip thereby and is therefore higher in cleaning ability than a cleaning blade formed of metal. For this reason, a cleaning blade formed of rubber or similar elastic material is predominant over one formed of metal. An image forming apparatus using an elastic cleaning blade is disclosed in, e.g., Japanese patent laid-open publication Nos. 2004-325621 and 2003-167492.
Today, an image forming apparatus of the type using toner, having a substantially spherical shape and produced by polymerization or similar technology, is known in the imaging art. It is generally accepted that substantially spherical toner (simply spherical toner hereinafter) promotes efficient image transfer more than conventional pulverized toner irregular in shape and can meet the increasing demand for higher image quality.
However, the problem with spherical toner is that it cannot be sufficiently removed from the surface of an image carrier by a conventional cleaning blade configured to remove pulverized toner, resulting in defective cleaning.